Strong and corrosion-resistant 3D-printed steel by self-assembled core-shell nanoparticles

Metal additive manufacturing often produces coarse columnar grains and elemental segregation, resulting in anisotropic mechanical properties and degraded corrosion resistance. We present a powder blending strategy using multicomponent carbides (MCCs) to overcome these limitations in 316L stainless steel. Upon dissolution, MCCs drive the self-assembly of uniformly distributed core-shell oxynitride-carbide nanoparticles, which sequester detrimental nitrogen/oxygen impurities and markedly refine austenite grain size from 43.9 to 2.1 micrometers. This unique microstructure control yields an excellent combination of strength and ductility. Crucially, the corrosion resistance is enhanced by suppressing chromium segregation via tungsten, niobium, and tantalum partitioning to the cell boundaries and facilitating the formation of a protective tungsten trioxide-rich passive film. This work establishes an instructive paradigm for metal additive manufacturing, demonstrating how MCCs' introduction can tailor nanoprecipitations, grain structure, and alloy chemistry to simultaneously improve strength and corrosion resistance in structural alloys.